Aromatic diisocyanates are raw materials of many useful polymers such as aromatic polyurethanes, aromatic polyamides, aromatic polyimides, aromatic polyureas, aromatic polycarbodiimides, etc.
In these aromatic diisocyanates, a compound which is somewhat structurally relevant to the compound of the present invention is a compound represented by following formula (6) disclosed in JP-A-1-132553 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"): ##STR1## wherein R.sub.8 and R.sub.9 each represent a lower alkyl group having from 1 to 4 carbon atoms or a halogen atom, and x and y each represent an integer of from 1 to 4.
Further, U.S. Pat. No. 4,017,459 discloses in Example 12 an aromatic diisocyanate represented by following formula (7): ##STR2##
However, these aromatic diisocyanate compounds greatly differ from the compound of the present invention represented by formula (1) described hereinbelow in the chemical structure. Further, since polymers which use these conventional aromatic diisocyanates as the raw materials generally have high melting point, melt molding of these polymers is difficult or film forming from these polymer solutions is difficult because they have low solubility to organic solvents. Also, it may be in general difficult to produce polymers having high degree of polymerization using these aromatic diisocyanates. To obtain mechanical properties suitable for films and moldings, divalent aromatic residues in a polymer skeleton must be para-linked. However, such a polymer skeleton has the disadvantage that the skeleton has a rigidity and also has a poor flexibility. Further, since such an aromatic diisocyanate has a low melting point and a poor crystalline property, there are problems that the isolation and purification thereof are difficult and even when the aromatic diisocyanate is obtained as a solid, the diisocyanate is easily hydrolyzed into an aromatic diamine. Accordingly, there is a problem that when a polymerization reaction is carried out using such an aromatic diisocyanate as a monomer, a high polymer may not be obtained or a side-reaction may occur.